In order to improve the wear resistance of friction parts made of C/C composite material, proposals have been made to introduce a refractory ceramic therein, and in particular silicon carbide, SiC.
Thus, according to document WO 99/23049, a fiber preform made of carbon fibers is impregnated with a colloidal solution of a refractory oxide such as silica SiO2, which oxide is transformed into carbide by heat treatment, thereby giving rise to a reaction between the oxide and the carbon of the preform fibers. The preform is then densified with a carbon matrix by chemical vapor infiltration (CVI).
In document U.S. Pat. No. 6,376,431, proposals are made to impregnate the fiber preform with a solution of a ceramic precursor, such as an SiC precursor, and then to perform heat treatment to ceramize the precursor prior to densification with a carbon matrix by CVI.
Document WO 2006/067184 in the name of the Applicant, describes a method comprising impregnating two-dimensional textures or fiber plies made of carbon fibers with a solution or a suspension that makes it possible, after a three-dimensional fiber preform has been made from the two-dimensional textures or plies, to obtain an impregnated fiber preform. The solution or suspension is a sol-gel that is a precursor of a refractory oxide such as SiO2, or a colloidal suspension of an oxide, such as colloidal silica. Heat treatment for converting the oxide into carbide by reacting with the carbon of the fibers is performed prior to densification with a carbon matrix by CVI.
The Applicant has observed that the presence of ceramic particles does indeed enable friction wear to be reduced, however it affects the mechanical properties of the resulting C/C composite material friction part. The method of document WO 2006/067184 seeks to attenuate that effect of the presence of ceramic particles by enabling the distribution of ceramic particles within the part to be controlled, in particular in order to avoid having such particles present in zones that are subjected to high levels of mechanical stress, such as the cores of brake disks that serve to transmit braking torque.